BLOCK: 5 H.P. Briggs & Stratton Engine Only. Machining for clearance for rod, cam, and lifters are allowed. 2.630" maximum bore size. Welding to strengthen lifter bore and to repair broken rod damage areas only. No welding from cooling fins upwards.
BLOCK DECK SURFACE: Piston pop-ups is non-tech. Head gasket surface and top of block are non-tech items.
VALVES & SEATS: Steel valve seats only size and shape are non-tech. Aftermarket stainless or steel valves only, no titanium. Intake valve diameter 1.140" maximum. Exhaust valve diameter 1.005" maximum. Springs are non-tech item. No titanium retainers.
CAM: .400" maximum lift. Checked at the valve with springs attached as run.
PORTS: Porting is allowed. Port surfaces are non-tech. No addition of any materials to ports. No holes in ports. No machining of gasket mating surfaces on intake or exhaust.
CARBURETORS: Option #1; Briggs Raptor .715 bore with stock tank. No additional material may be added other than to block choke and vent holes.
Option #2; Animal Carb or Keihin carb (part #JH90) as cast from factory. Venturi maximum .792" vertical, .605" and .618" horizontal WKA animal no-go guages may enter but may not pass through bore. Items that can be removed through fuel bowl including nozzle are non-tech items.
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